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Goa Chemical https://goachemical.com/product/screen-printing-photography-chem/ Export date: Wed Sep 2 2:35:03 2026 / +0000 GMT  |
Screen Printing Photography ChemSKU: RXSOL-18-1016-025
Product DescriptionThis materials have important uses in photography 3 1 and in photographic screen printing 4 2, where it is used as an oxidizing agent together with a strong mineral acid. Potassium dichromate has important uses in photography 3 1and in photographic screen printing 4 2, where it is used as an oxidizing agent together with a strong mineral acid. Gum bichromate 5printing was one of the very first stable photographic printing processes, dating back to about 1850. A solution of gum arabic 6and potassium dichromate, once applied to paper and dried, will harden when exposed to ultraviolet light. Chromium intensificationor Photochromos uses potassium dichromate together with equal parts of concentrated hydrochloric acid 7diluted down to approximately 10% v/v to treat weak and thin negatives of black and white photograph roll. This solution reconverts the elemental silver particles in the film to silver chloride 8. After thorough washing and exposure to actinic 9light, the film can be redeveloped to its end-point yielding a stronger negative which is able to produce a more satisfactory print. A potassium dichromate solution in sulfuric acid 10can be used to produce a reversal negative (i.e., a positive transparency from a negative film). This is effected by developing a black and white film but allowing the development to proceed more or less to the end point. The development is then stopped by copious washing and the film then treated in the acid dichromate solution. This converts the silver 11metal to silver sulfate 12, a compound that is insensitive to light. After thorough washing and exposure to actinic light, the film is developed again allowing the previously unexposed silver halide to be reduced to silver metal. The results obtained can be unpredictable, but sometimes excellent results are obtained producing images that would otherwise be unobtainable. This process can be coupled with solarisation 13so that the end product resembles a negative and is suitable for printing in the normal way. CrVI compounds have the property of tanning 14animal proteins 15when exposed to strong light. This quality is used in photographic screen-printing 19 17 16. In screen-printing 19 17 16a fine screen of bolting silk or similar material is stretched taut onto a frame similar to the way canvas is prepared before painting. A colloid 18sensitized with a dichromate is applied evenly to the taut screen. Once the dichromate mixture is dry, a full-size photographic negative is attached securely onto the surface of the screen, and the whole assembly exposed to strong light - typically about half an hour in bright sunlight - hardening the exposed colloid. When the negative is removed, the unexposed mixture on the screen can be washed off with warm water, leaving the hardened mixture intact, acting as a precise mask of the desired pattern, which can then be printed with the usual screen-printing 19 17 16process.
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Product added date: 2019-09-13 09:26:19 Product modified date: 2019-09-13 09:26:21 |
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Export date: Wed Sep 2 2:35:03 2026 / +0000 GMT Product data have been exported from Goa Chemical [ http://goachemical.com ] Product Print by WooCommerce PDF & Print plugin. |
